Polyurethane compositions are prepared from polyols and polyisocyanates. Depending upon the properties desired for the polyurethane, the polyols will be of varying molecular weight ranging from as little as 62 for ethylene glycol and up to several thousand for the polymeric polyols.
In addition to being quite viscous, the higher molecular weight polyols generally are relatively expensive. Likewise, the polyisocyanates are generally expensive. In order to improve the handling characteristics of the polyols and, more importantly, to reduce the cost of the polyurethane material obtained, the polyols prior to being reacted with the polyisocyanate are generally blended with an inert extender. The extenders are usually substantially non-volatile, medium viscosity oils or cut-back asphalts. Adding these materials to the polyols substantially reduces their viscosity, thereby making them easy to handle.
When these lower viscosity polyurethane forming compositions are applied to surfaces such as floors, they flow rather easily and are self-leveling. This is a highly advantageous property except when the surface to which the polyurethane is applied is not level. For example, running tracks often have banked turns of up to 5%, generally 2-3%, slope. When polyurethane compositions are applied to these slopes, they tend to slump and run off. Obviously this is not an acceptable situation. Furthermore, it is often desirable to apply polyurethane compositions to areas having greater slopes than this and even to walls and ceilings. However, it is also desirable to have compositions which are easily handled (e.g., liquids which can be pumped, etc.) thereby allowing easy installation.